Calibrating Multi-Dimensional Sensor for Offset, Sensitivity, and Non-Orthogonality

1. A method comprising: collecting raw data for a plurality of axes of a multi-dimensional sensor and providing the collected raw data to a processor; iteratively determining at least one of ellipse parameters and ellipsoid parameters using the raw data and at least one of previously determined ellipse parameters and previously determined ellipsoid parameters, wherein iteratively determining at least one of ellipse parameters and ellipsoid parameters using the raw data uses a cyclic Jacobi sweep; calculating with the processor an offset calibration factor for each of the plurality of axes of the multi-dimensional sensor based on the at least one of the ellipse parameters and the ellipsoid parameters; calculating with the processor a sensitivity calibration factor for each of the plurality of axes of the multi-dimensional sensor based on the calculated offset calibration factor and the at least one of the ellipse parameters and the ellipsoid parameters; calculating with the processor a non-orthogonality calibration factor for one or more pairs of axes of the multi-dimensional sensor based on the calculated offset calibration factor, the calculated sensitivity calibration factor and the at least one of the ellipse parameters and the ellipsoid parameters; storing the calculated offset calibration factors, the sensitivity calibration factors and one or more non-orthogonality calibration factor in memory coupled to the processor; and correcting raw data for the plurality of axes of the multi-dimensional sensor with the processor using the stored calculated offset calibration factors, the sensitivity calibration factors and the one or more non-orthogonality calibration factor.

2. The method of claim 1 , wherein the multi-dimensional sensor is a magnetometer and the raw data is collected outside a presence of a disturbing magnetic near field.

3. The method of claim 1 , wherein the multi-dimensional sensor is an accelerometer and the raw data is collected while the accelerometer is subjected to no acceleration beyond gravity.

4. The method of claim 1 , wherein: the offset calibration factor for each of the plurality of axes of the multi-dimensional sensor compensates for at least an offset along each axis of the multi-dimensional sensor; the sensitivity calibration factor for each of the plurality of axes of the multi-dimensional sensor compensates for at least a sensitivity of each axis of the multi-dimensional sensor, the sensitivity of each axis being dissimilar; and the non-orthogonality calibration factor for the one or more pairs of axes of the multi-dimensional sensor compensates for misalignment between the one or more pairs of axes of the multi-dimensional sensor.

8. The method of claim 7 , wherein the raw data for the plurality of axes of the multi-dimensional sensor are corrected as follows: B ^ ⁢ ⁢ cal = ( pinv ⁡ ( R ) * diag ⁡ ( 1. / scale ) * [ ( B x - off x ) ( B y - off y ) ( B z - off z ) ] ) where {circumflex over (B)}cal is the corrected raw data and R is matrix as follows: R = [ 1 ψ θ ψ 1 ϕ θ ϕ 1 ] .

11. The method of claim 10 , wherein the raw data for the plurality of axes of the multi-dimensional sensor are corrected as follows: B ^ ⁢ ⁢ cal = ( pinv ⁡ ( R ) * diag ⁡ ( 1. / scale ) * [ ( B x - off x ) ( B y - off y ) ] ) where {circumflex over (B)}cal is the corrected raw data and R is matrix as follows: R = [ 1 ψ ψ 1 ] .

12. A mobile station comprising: a multi-dimensional sensor that provides raw data for each of a plurality of axes; a processor connected to the multi-dimensional sensor, the processor receives from the multi-dimensional sensor the raw data for each of the plurality of axes; memory connected to the processor; and software held in the memory and run in the processor to calibrate the multi-dimensional sensor, the software including instructions to iteratively determine at least one of ellipse parameters and ellipsoid parameters using the raw data and at least one of previously determined ellipse parameters and previously determined ellipsoid parameters wherein the software includes instructions to iteratively determine at least one of ellipse parameters and ellipsoid parameters using the raw data using a cyclic Jacobi sweep, to calculate and store in the memory an offset calibration factor for each of the plurality of axes based on the at least one of the ellipse parameters and the ellipsoid parameters; to calculate and store in the memory a sensitivity calibration factor for each of the plurality of axes based on the calculated offset calibration factor and the at least one of the ellipse parameters and the ellipsoid parameters; and to calculate and store in the memory a non-orthogonality calibration factor for one or more pairs of axes based on the calculated offset calibration factor, the calculated sensitivity calibration factor and the at least one of the ellipse parameters and the ellipsoid parameters; the software further including instructions to correct the raw data for each of the plurality of axes using the stored calculated offset calibration factors, the stored sensitivity calibration factors and the stored one or more non-orthogonality calibration factor.

13. The mobile station of claim 12 , wherein the multi-dimensional sensor is at least one of a magnetometer and an accelerometer.

14. The mobile station of claim 12 , wherein: the offset calibration factor for each of the plurality of axes of the multi-dimensional sensor compensates for at least an offset along each axis of the multi-dimensional sensor; the sensitivity calibration factor for each of the plurality of axes of the multi-dimensional sensor compensates for at least a sensitivity of each axis of the multi-dimensional sensor, the sensitivity of each axis being dissimilar; and the non-orthogonality calibration factor for the one or more pairs of axes of the multi-dimensional sensor compensates for misalignment between the one or more pairs of axes of the multi-dimensional sensor.

18. The mobile station of claim 17 , wherein the software includes instructions to correct the raw data for each of the plurality of axes using the stored calculated offset calibration factors, the stored sensitivity calibration factors and the stored one or more non-orthogonality calibration factor as follows: B ^ ⁢ ⁢ cal = ( pinv ⁡ ( R ) * diag ⁡ ( 1. / scale ) * [ ( B x - off x ) ( B y - off y ) ( B z - off z ) ] ) where {circumflex over (B)}cal is the corrected raw data and R is matrix as follows: R = [ 1 ψ θ ψ 1 ϕ θ ϕ 1 ] .

21. The mobile station of claim 20 , wherein the software includes instructions to correct the raw data for each of the plurality of axes using the stored calculated offset calibration factors, the stored sensitivity calibration factors and the stored one or more non-orthogonality calibration factor as follows: B ^ ⁢ ⁢ c ⁢ ⁢ al = ( pinv ⁡ ( R ) * diag ⁡ ( 1. / scale ) * [ ( B x - off x ) ( B y - off y ) ] ) where {circumflex over (B)}cal is the corrected raw data and R is matrix as follows: R = [ 1 ψ ψ 1 ] .

22. A mobile station comprising: means for collecting raw data for a plurality of axes of a multi-dimensional sensor; means for iteratively determining at least one of ellipse parameters and ellipsoid parameters using the raw data and at least one of previously determined ellipse parameters and previously determined ellipsoid parameters, wherein iteratively determining at least one of ellipse parameters and ellipsoid parameters using the raw data uses a cyclic Jacobi sweep; means for calculating an offset calibration factor for each of the plurality of axes of the multi-dimensional sensor based on the at least one of the ellipse parameters and the ellipsoid parameters; means for calculating a sensitivity calibration factor for each of the plurality of axes of the multi-dimensional sensor based on the calculated offset calibration factor and the at least one of the ellipse parameters and the ellipsoid parameters; means for calculating a non-orthogonality calibration factor for one or more pairs of axes of the multi-dimensional sensor based on the calculated offset calibration factor, the calculated sensitivity calibration factor and the at least one of the ellipse parameters and the ellipsoid parameters; and means for correcting raw data for the plurality of axes of the multi-dimensional sensor using the calculated offset calibration factors, the sensitivity calibration factors and the one or more non-orthogonality calibration factor.

23. The mobile station of claim 22 , wherein the multi-dimensional sensor is at least one of a magnetometer and an accelerometer.

24. The mobile station of claim 22 , wherein: the offset calibration factor for each of the plurality of axes of the multi-dimensional sensor compensates for at least an offset along each axis of the multi-dimensional sensor; the sensitivity calibration factor for each of the plurality of axes of the multi-dimensional sensor compensates for at least a sensitivity of each axis of the multi-dimensional sensor, the sensitivity of each axis being dissimilar; and the non-orthogonality calibration factor for the one or more pairs of axes of the multi-dimensional sensor compensates for misalignment between the one or more pairs of axes of the multi-dimensional sensor.

28. The mobile station of claim 26 , further comprising a means for correcting the raw data that corrects the raw data as: B ^ ⁢ ca ⁢ ⁢ l = ( pinv ⁡ ( R ) * diag ⁡ ( 1. / scale ) * [ ( B x - off x ) ( B y - off y ) ( B z - off z ) ] ) where {circumflex over (B)}cal is the corrected raw data and R is matrix as follows: R = [ 1 ψ θ ψ 1 ϕ θ ϕ 1 ] .

31. The mobile station of claim 30 , further comprising a means for correcting the raw data that corrects the raw data as: B ^ ⁢ ca ⁢ ⁢ l = ( pinv ⁡ ( R ) * diag ⁡ ( 1. / scale ) * [ ( B x - off x ) ( B y - off y ) ] ) where {circumflex over (B)}cal is the corrected raw data and R is matrix as follows: R = [ 1 ψ ψ 1 ] .

32. A non-transitory computer-readable medium including program code stored thereon, comprising: program code to iteratively determine at least one of ellipse parameters and ellipsoid parameters using collected raw data and at least one of previously determined ellipse parameters and previously determined ellipsoid parameters, wherein the program code to iteratively determine at least one of ellipse parameters and ellipsoid parameters using the collected raw data uses a cyclic Jacobi sweep; program code to calculate an offset calibration factor for each of a plurality of axes of a multi-dimensional sensor based on the at least one of the ellipse parameters and the ellipsoid parameters for the plurality of axes of the multi-dimensional sensor; program code to calculate a sensitivity calibration factor for each of the plurality of axes of the multi-dimensional sensor based on the calculated offset calibration factor and the at least one of the ellipse parameters and the ellipsoid parameters for the plurality of axes of the multi-dimensional sensor; program code to calculate a non-orthogonality calibration factor for one or more pairs of axes of the multi-dimensional sensor based on the calculated offset calibration factor, the calculated sensitivity calibration factor and the at least one of the ellipse parameters and the ellipsoid parameters for the plurality of axes of the multi-dimensional sensor; and program code to correct raw data for the plurality of axes of the multi-dimensional sensor using the calculated offset calibration factors, the sensitivity calibration factors and the one or more non-orthogonality calibration factor.

36. The non-transitory computer-readable medium of claim 35 , wherein the program code to correct the raw data corrects the raw data as: B ^ ⁢ ca ⁢ ⁢ l = ( pinv ⁡ ( R ) * diag ⁡ ( 1. / scale ) * [ ( B x - off x ) ( B y - off y ) ( B z - off z ) ] ) where {circumflex over (B)}cal is the corrected raw data and R is matrix as follows: R = [ 1 ψ θ ψ 1 ϕ θ ϕ 1 ] .

39. The non-transitory computer-readable medium of claim 38 , wherein the program code to correct the raw data corrects the raw data as: B ^ ⁢ ca ⁢ ⁢ l = ( pinv ⁡ ( R ) * diag ⁡ ( 1. / scale ) * [ ( B x - off x ) ( B y - off y ) ] ) where {circumflex over (B)}cal is the corrected raw data and R is matrix as follows: R = [ 1 ψ ψ 1 ] .